U.S. Pat. No. 7,281,694 B2, granted to Allen et al., discloses a rack, or more specifically an equipment rack, including a plurality of posts, or vertical support columns (104), arranged in a bilaterally symmetric manner. An object, or rack-mount module (102), is mounted on the left and right vertical support columns (104) of the equipment rack via the mounting brackets (114) on a pair of slide rail assemblies and is thus mounted on the equipment rack. More specifically, in the embodiment shown in FIG. 4A to FIG. 4C of the specification of the afore-cited patent, a mounting bracket (200) has a base member (202) with a cantilevered flat spring (214). While the base member (202) of the mounting bracket (200) is being mounted to a vertical support column (104), the cantilevered flat spring (214) abuts against an end portion of the vertical support column (104) and is tilted by an angle toward a side plate (204) of the base member (202) so that a pin (210) on the base member (202) can be aligned with and mounted into a hole (106) of the vertical support column (104). Once the pin (210) is in place, the cantilevered flat spring (214) resumes the unbiased position and abuts against the vertical support column (104).
In an actual mounting operation, however, the mounting bracket on the slide rail assembly must be correctly mounted on the left or right side of the equipment rack in order to mount the rack-mount module properly into the rack. It is, therefore, common practice nowadays for slide rail assembly manufacturers to mark their products, either the slide rails or the brackets on them, with the letter “L” or “R” to facilitate identification of the particular side (i.e., left or right) for which a slide rail or bracket is intended. Nevertheless, a marked slide rail or bracket may still be mounted on the wrong side of a rack due to the operator's negligence, resulting in an error in installation or even endangering the operator and the equipment in question. The present invention was developed to solve this very problem of the prior art.